In a cutting tool used for internal machining operations, a cutting insert with a single cutting portion is removably secured to an insert holder. The cutting insert has two opposing end surfaces, and an insert peripheral surface extending therebetween having three spaced apart abutment surfaces. The insert holder has a holder portion with a holder peripheral surface and an adjacent seating surface. At least one protuberance having four spaced apart reaction surfaces protrudes from the seating surface. The cutting insert is securable to the holding portion in left-hand and right-hand assembly positions, with the three abutment surfaces in clamping contact with three of the four reaction surfaces. In the left-hand assembly position, a first end surface is in clamping contact with the seating surface, and in the right-hand assembly position, a second end surface is in clamping contact with the seating surface.